By means of its solenoid valves, a pilot control unit activates an air-flow-boosting relay valve, which, in turn, can activate one or more ducts. For use in an electropneumatic brake system, such as, for example, an electronically regulated brake system (EBS) for trailers, wheel-brake modules having brake cylinders for the wheel brakes are activated by the relay valve.
DE 100 09 116 A1 describes a pilot control unit for a brake pressure modulator in a trailer having an electronic brake system. The solenoid valves are constructed as cartridge solenoid valves, whose valve cartridges are placed in a housing having a solenoid. First, this solenoid is introduced into the housing, and, then, the valve cartridge is inserted in an assembly direction into the housing and joined to the housing. The pilot control unit is provided with a pneumatic and an electrical interface.
DE 10 2004 035 763 A1 describes a valve control device that is preferably provided as a valve control unit for two brake ducts of an electro-pneumatic brake system. It has three valve units, each of which is designed as a valve modulator device for a brake pressure regulating circuit; in this case, an air admission valve is provided with a primary armature and a vent valve is provided with a secondary armature, the two magnet armatures having a common armature guide arrangement and a common solenoid system and being switched at different current intensities. Thus, air can be admitted to the downstream wheel module, the input pressure can be held and venting can be achieved by means of a common solenoid system.
However, such valve control units of pilot control units generally have complex structures and require a large installation space. In particular, the manufacture of a main housing and further components as well as the pneumatic passage of air through diverse air ducts, seals and possibly tubes between the various components is time-consuming and laborious. Mounting of the solenoids and pressure sensors as well as contacting with the electronics via the separate interfaces is also time-consuming and laborious.
In the case of a defect of the sensors, valves or electronics, the entire valve control unit must then be replaced.